Retune after building bottom end?

[motteramm]

Ok. This is probably a noob question and I feel stupid for asking it, but I have searched. I have talked to local tuners and engine builders about weather or not I will need to retune my KA-T after building the bottom end. Some have told me it will be fine others have said I need to redo everything. I have a very basic KA-T setup, t-25 370cc SR injectors 8lbs on a JWT ecu. Currently my block is all stock. Now I'm putting the car down this Christmas to build the bottom end with forged pistons and rods (keeping stock compression ratio) and was wondering if I need to retune it or just drive it around and check to my AFR's? Again flame suit on dumb question.

[mechanicalmoron]

If it was tuned when worn, like 155 compression or something, I think you'd want to, because stock compression is 179. It depends why you messed with it I guess.

[JKTUNING]

If we are talking about a JWT reflash or mail order tune, then there isn't too much they are going to do just for swapping out a set of pistons with the same compression ratio.

BUT if you are actually tuning your car yourself or by a tuner, then it isn't a bad idea to have it checked over. It is never fun to damage a new motor because something isn't quite right and stuff like that is most easily found when the car is either on the dyno or in a competent tuner's hands.

[steve shadows]

There is nothing wrong with tuning it yourself but you'll definitely need an EMS. I used to dyno tune everyone's car but honestly if you have the properly built timing map loaded in an EMS that is built based on past dyno history and VE you can get it very close to optimal remotely. Then you're just polishing up the fuel map on the dyno. I suggest upgrading to an AEM unit or a Haltech though if you're going to get serous.